This invention relates to insect control through the application of insecticide and, particularly, to an improved system and method for applying insecticide from a vehicle to more accurately, safely and cost-effectively eradicate mosquitoes in both rural and city environments.
Prior to 1990, open-loop, electronic-based fluid flow rate control was available to the mosquito control industry. The earliest device of this type was the xe2x80x9cPRO-FLO,xe2x80x9d a proportional flow rate pump controller invented by H. Starr (deceased). Currently available mosquito insecticide delivery systems utilize aerosol (i.e., fog) generators mounted on a prime mover, such as a truck or other vehicle, to enable spraying to specifically selected sites in rural and city environments. The majority of these systems typically employ a small gas motor, a blower unit for generation of an air flow, a supply tank for the insecticide and a nozzle assembly which mixes the insecticide chemical with the blower-directed air in order to disperse the insecticide as micron size insecticide fog particles. Recently, a different class of aerosol generators have become available which use electrical power to generate the insecticide fog. While the spray results for electrical power generators are similar to the gas powered spray systems, they are significantly quieter during spraying.
Often, the ground vehicle spraying systems are used together with insecticide spraying via aircraft as part of a comprehensive program to eradicate mosquitoes.
Since mosquito bites can lead to very serious infections (malaria, dengue fever and encephalitis), the requirement for ground vehicle mosquito eradication programs will continue indefinitely. Further, the increase in the average temperature in both the winter and summer months (due to CO2 and other greenhouse gases) will steadily increase both the areas and time periods each year when mosquito eradication programs will be required. A recent example of this increased need for a mosquito eradication program occurred during 1999 in New York City. Mosquito bites resulted in several cases of encephalitis and consequentially a new comprehensive and continuing mosquito eradication program has been implemented for that city.
One major problem associated with presently available ground vehicle mosquito spray systems is that the weather conditions locally at the vehicle are not automatically considered in the spray process. At present, the vehicle operator must decide whether to stop or continue the spray process if obvious weather problems such as heavy rain exist. However, the vehicle driver in an enclosed air-conditioned vehicle cab may not be aware of other adverse weather conditions such as wind speed and direction. For example, if the wind on a city street is blowing at 90 degrees to the direction of vehicle travel, then one side of the street will receive more insecticide concentration and the opposite side of the street will receive less than planned. Further, particular weather conditions at a spray vehicle may mean that the spraying must fully stop or that the vehicle must travel in a different direction than planned to achieve a desirable spray application in a particular area.
Unfortunately, the information on weather related discrepancies in spray coverage are not presently available to management. Therefore, no corrective action can be taken for the level of insecticide concentration varying widely over a spray process. In addition, the humidity level and the ground temperature at the vehicle also impact the fog distribution process. These two variables along with wind and vehicle velocity should also be considered continuously to optimize the spraying process. The control interaction with these complex variables during a spray operation requires an electronic recorder and controller system with the capability to both process intelligent spray control algorithms and record and utilize real-time weather information. Effective spray systems with these capabilities have not previously been available.
Such intelligent spray control algorithms are also dependent upon accurate knowledge of the vehicle geographical position. For example, the decision to spray at a certain concentration (or not spray at all) may depend upon geographical information such as (a) the location of insecticide sensitive individuals or animals in the planned spray area, and/or (b) the location of areas which have a high potential for mosquitoes such as a stagnant pond. Fortunately, the required accurate geographical knowledge is now universally available to all vehicles in real-time and at low cost to the electronic recorder and controller system via inputs from the U.S. Global Positioning Satellite System (GPS).
Another major problem with presently available aerosol generators is the difficulty of both generating and verifying the desired droplet size of the insecticide. A desired particle size must be maintained while providing varying fluid flow rates, which are required in order to maintain the same concentration of insecticide as the vehicle varies its speed while spraying. The droplet size for a particular chemical and the maximum application rate per unit area are determined from regulations by the U.S. Environmental Protection Agency and/or state and local governments. The regulations for droplet size are based upon conflicting requirements of the effect of the insecticide upon the general environment and the need for a maximum effective kill rate for the insecticide. The optimum particle size will vary for a particular chemical, for a particular location and for weather conditions, as well as the type of target mosquito.
The presently available spray technology assumes that the desired particle size can be generated by varying the air pressure applied to the nozzle against a measured fluid flow rate. This technique requires a series of calibrations of particle size versus air pressure and fluid flow rate for each insecticide type. This control of air pressure applied to the nozzle for mosquito eradication is implemented in the mosquito control industry by two prior art methods, the most common of which is a one-point calibration of a fixed air pressure setting versus a fixed flow rate for a particular chemical. This technique is an open-loop control process that produces a desired particle size only at a fixed fluid flow rate and at the related vehicle speed. As the vehicle speed varies during a spray application, the particle sizes may vary widely from the particle size specified in government regulations. The second method requires the addition of an air pressure sensor, a pressure regulator valve and a controller to maintain a desired air pressure relative to the vehicle speed and the fluid flow rate. While requiring more equipment and extensive calibrations, this method is still an open loop approach as the particle size can vary during a spray process and not be detected. An example of this method is disclosed in U.S. Pat. No. 5,248,448 to Waldron et al.
For electrically powered spray systems of the type described above, the particle size is generated by the rotation rate of a porous cylinder block located on the rotating shaft. Changes in the particle size is accomplished by varying the rotation rate of the shaft. This technique is still an open loop control system for particle size.
In order to correct these serious problems in vehicle mosquito spray systems, there is a need for a new system and method which:
(1) Continuously maintains the optimum mosquito insecticide droplet size and application rate;
(2) Continuously includes the weather conditions at the vehicle as part of the spray control process;
(3) Continuously includes the geographical position of the vehicle as part of the spray control process;
(4) Accepts programmable spray process instructions and provides detailed spray process reports including the concentration of insecticides applied at any time and/or at a geographical position; and
(5) Is flexible in design so as to be adaptable for controlling insecticide particle size and recording data based upon other criteria.
The present invention is directed to a system and method which provides these and other features.
A primary objective of this invention is to provide an improved ground vehicle mosquito insecticide spray system and method which ensures that the desired spray flow rate at the optimum particle size is effectively applied to the selected area.
Another object of this invention is to provide an insecticide delivery system and method which utilizes a closed loop control approach based upon direct, real-time measurement of the insecticide particle size being delivered by the sprayer.
It is another object of the present invention to provide a system and method which supplies detailed reports on the estimated spray application concentrations for all geographical locations that have been exposed to insecticide spraying.
It is another object of the invention to provide real-time insecticide particle size measurement data to a Sprayer Recorder and Controller (SRC) unit so that real-time control of the particle size can be achieved.
It is another object of the invention to use a system and method which provides local weather information (wind velocity, humidity and temperature for example) automatically to the vehicle SRC so that this information can be used in real-time in the spray control process. This information is also be reported as part of the process of accessing the viability of a particular insecticide at a specific location.
It is another object of the invention for the SRC to accept geographical position information and related instructions so that real-time control of the spray process in selected geographical positions is automatically achieved.